What the difference if the water passed through the shell and the hot air (with same inlet temperature and mass flow rate) are passed through the tubes ?
There might be some difference in the performance of the exchanger but the long term problem could be difficulty with fouling on the side from the water. The overall heat transfer coefficient could be affected by the differences in the velocity of the two fluids. The pressure drop could also be affected with the reversal of two fluids. It would take a rigorous calculation to determine the actual change in exchanger performance. Water is typically put on the tube side for ease of cleaning the tubes that can be fouled by deposits from the water impurities.
Nothing. ENERGY cannot be created or destroyed. Everything would balance out. Corrosion wise, unless the inner material of the heat exchanger is different from the outer, then it should be ok
It wouldn't work as well because air isn't a great heat conductor. Additionally, you might fry and short circuit some components. However, if it worked, you'd get the reverse of what the heat exchanger normally did. If the water usually gets cold, then the air would get cold. If the water usually gets hot, then the air would get hot, etc.
